An Easy way to install bigger batteries.

The Hymer, and most motorhomes, has a battery box that will take 2 batteries - one for the engine and one for the van - the leisure battery (LB). If you want more power, then you have to locate the LB elsewhere.

It's not a good idea to just slap an additional battery elsewhere and wire it in in parallel, although many people do just that, usually because there is very little choice and it's the easy way out. But you will never get the full potential out of two batteries installed in this way.

But you soon understand the problem when you decide to do it properly, and install 2 or more identical batteries elsewhere in the van - how do you wire them in? All the connections go to the original battery box, where the original LB is!

The easy answer is to use a "dummy battery" and big thick cables.

Take out the original LB, and replace it with a piece of wood with two terminal blocks mounted on it - one for pos one for neg. Then attach all the wires that used to go to the pos of the LB to the pos side, and ditto for the neg side.

So now you have all the wires connected as they were, but no battery!

Install the new battery(s) wherever suitable in your van. In an S700 there is little choice - it's either in the boot or in the gas locker. Another possibility if you are handy is to make an under chassis battery box - as found in HGVs. But wherever you put them, they must be identical, and wired in parallel. 

Then you take a single thick wire - as thick as you can afford and work with - I suggest 10 to 12mm diameter - and run it from the battery, down through the floor, along the underside of the van, and up into the original battery box, and to the positive terminal block on the dummy battery.

Now all you need to do is connect the negatives. You have two choices - you can run a separate wire along with the positive one, or you can use chassis, which saves wire - thick wire is expensive. You will see from your original battery box that the neg of both batteries goes to chassis via thick black cables. So attach the original LB neg to the neg terminal block. At the other end at the new batteries, run a thick cable to the nearest point on the chassis - make sure it's a clean connection to the main chassis member - usually down through the floor. 

IMPORTANT - do not connect the chassis neg to the same battery neg as the positive if more than one battery. It must go to the opposite neg of the last battery in the pack. So if two LB's in parallel, then the neg goes to the neg of the second battery.  This keeps the system balanced, and multiple batteries are seen "as one". The rule is - pos to the pos of the first battery, neg to the neg of the last battery. (does not apply for only one battery)

And that's it basically! No modifications to original van wiring needed at all. You can tap solar into the pos wire and neg to chassis at any convenient point, and the same if you upgrade your charger as you should if you install bigger batteries. The space where the LB used to be is now a useful empty space, you can put a charger or an inverter in there, whatever you can fit. Usually you would install your charger, inverter and solar controller as close to the batteries as possible.


Dummy battery - a simple piece of wood with two terminal blocks, in place of the original LB. You can see the original thick black cable going to the neg of the starter battery, and at the bottom you can see the thick red cable that goes down out of the box, and off to the new batteries. - not needed for most installations.

The little red box is a split charge relay- not needed for most installations.


Here is an install I did using 4 x 100a/h batteries. NOTE - the colours are wrong - the lower right connection to the neg is red - it should be black - to chassis. (wire is expensive - I had no black left) But everything else is correct. The pos is top left, and the main pos wire back to the original battery box goes from here. The blue box is a Victron inverter charger, and the white is a new consumer unit, but usually you would use the original 240v consumer unit to supply 240v from your inverter tom the van plugs.

Important NOTE!! This installation of 4 batteries in the boot of an S700 proved after one year to be too heavy. Pay attention to weight distribution. See next blog post on how I solved it. This photo is for demonstration of wiring batteries in parallel - not where to put them in your van.

More photos of some other dummy battery installs I have done.

The relay on the left is Victron Cyrix intelligent relay. It replaces the Hymer split charge relay (R1) which is located behind the fuse panel. It is important to take out R1 if you fit the Cyrix. The reason for this is that the Hymer wiring and relay is only rated to pass about 20 amps of charge through to a normal single leisure battery. If you fit bigger batteries, you need more charge. Fitting a bigger relay, with thicker wiring, enables about 50 amps to get through to the Odyssey from the alternator.

The yellow thing in the middle is a 100 amp mega fuse, and a convenient bolt on way of safety fusing - there is another on the negative of the battery - so that in the event of a crash which shorted out either the wiring, a fuse will blow.

Another method of fusing using blade fuses.

Another view - a dummy battery board makes installing and fusing extras a dream.

Major battery upgrade

It was a mistake to put 160 kilos of batteries in the boot of my S700, and then add a 130kg scooter! The van never complained, but there was a gradual awareness that it was too light at the front. We all make mistakes!

So how do I get powerful batteries in the front of my Hymer, when there is no obvious place to put them? Easy says Peter Curry, take the gas bottles out of the gas locker, install an underslung gas tank, then install anOdyssey PC1800 200 amp hour battery, which only weighs 60kilos, in the now empty gas locker.

So that's what we did! I did the electrics, while Peter did the gas tank. And then when we had finished all that Peter installed a new dash board in 12mm ply which has stiffened up the front end a treat - in addition to being almost a work of art!

The costs have been reasonable, especially after the sale of the old batteries, which Justin snapped up for the Linnebago 900 - which being a 7 and a half tonner doesn't even notice the weight. And the old refillable gas bottles went to a guy for his newly imported 670.

Everybody happy, and the van handles a lot better - I can feel the difference just by walking around inside. And I still have more power than I can shake a stick at - I am greedy when it comes to power.

Tech specs - 

Out - 4 x 100ah Yuasa professional sealed lead acid batteries.
In - 1 x Odyssey PC 1800 AGM 200ah marine battery.

Inverter - Victron 12/1600/70 inverter charger with auto changeover.

Solar - 3 x 120w Kyocera panels + 30amp MPPT controller

Nasa BM1 - compact battery management computer with 100amp shunt.

Gas 

Out - 2 x Gas-it 11kg refillable bottles

In - Gas-it 30kg (60 litre) underslung gas tank with external fill point and LED level meter inside van.

For lovers of tech trivia when I press the lever on my toaster, the battery delivers 105 amps to the inverter for the 4 minutes it takes to make toast. On a sunny day the solar will put that back in under an hour! But some days I have Muesli ...

Finished locker - gas now underslung, and a free shoe shelf with every pack!

Battery in red, Victron in blue, all sitting nicely on a plywood floor in the ex gas locker. Cables enter bottom left corner - 2 x 240v along chassis to consumer unit, very thick 12v cable across van chassis to original battery box, earth direct to chassis, solar cables along chassis and up through floor and wardrobe to roof. At bottom of picture is grey solar controller, which normally sits on top of Victron.

Closeup of 100amp shunt as supplied with Nasa BM1 battery monitor. Note thickness of cables - but also note that I used what was available and my cables are probably a bit over the top. There are online calculators for 12v cable size - but use the thickest you can.

And here is a follow up I wrote about the BM1 ...

The final piece of the jigsaw! Today I finally finished what I consider to be the ultimate energy system (for me anyway!), with the installation of abattery management monitor. 

I can now track and measure every amp in and out, which now enables me to calculate with good accuracy exactly how much longer my batteries will last, and how long it will take to fully recharge them, by any means.

This is only achievable if everything goes through a single shunt installed on the negative side of the battery - the original Hymer system and meters are untouched and fully functional.

The top display is the battery management monitor, and the lower display is the solar controller display, which isn't strictly necessary now that I have the new monitor display, but I had it already and it looks pretty.

What I have already learned, is that I am using a significant amount of power just doing nothing, as much as 4 amps if I am careless, but usually more like 2. I have a lot of gear in the van, and I am amazed at how much power is consumed when it's all switched off! This can be as much as 20amps wasted overnight, or the difference between getting a full charge and a partial charge from the solar panels on a cloudy day, while out shopping. So I am now going to install isolation switches so that no power is consumed while sleeping, or when not in the van so that the maximum charge goes into the batteries from the panels. I can also now see exactly what consumes what - the TV, the music system, the computer, the lights ... it is really informative and interesting - well it is to an anorak like me anyway!

Not every van needs such a system, but we live in our van for half the year, and we like to have pretty much as much power and convenience as we would have in a house, which isn't possible with just a single leisure battery.

Now we have bigger batteries, solar panels and an inverter/charger, and a system that tells us exactly how much power we have left, which means we can plan our movements much more accurately.

When the sun starts shining again, I am looking forward to seeing just how much sun is needed for daily self sufficiency.

Display of BM1 - top and Solar controller - bottom. Once you have a shunt which measures every amp in and out, then the BM1 can calculate the exact state of charge of your battery - you programme in the a/h capacity into the BM1 on installation. The top left photo shows 105% and 199 hours - which means it is fully charged.

And finally a quick and dirty schematic of the whole thing

Turbo conversions

http://www.wildcamping.co.uk/forums/show-us-your-van-motorhome/40941-yes-possible-fit-turbo-into-old-hymer-but-do-i-recommend-no.html

On LED lighting

Ron's Technical Tips No. 2.3 Amps

LED's - an alternative view.

Based on my own experience, and on reading pretty much every post on here since the beginning, I am starting to feel slightly negative about LED lighting, or at least about about installing them everywhere.

There are two main reasons for this - the first is how they look and feel - the aesthetics of them, and the second is just how much power do they really save?

Don't get me wrong, I like my LED installation, but it has taken me several years and at least 3 separate designs to get it to my satisfaction, and my present installation is in addition to and not instead of the original Hymer lighting. 

The first mistake I made was thinking that all leds are the same. They are not. I had to learn about "colour temperature", and that there are many, many shades of white. Several years ago it was difficult to know what you were buying, but now the market has settled down into roughly 2 shades of white - "cool white" and "warm white". Most people know this nowadays, but it is worth saying for the sake of completeness. Cool white is very bright and has shades of blue, and warm white has more yellow. It's down to personal taste, but in general most comments I have read indicate that warm is the way to go in a van, and cool is too harsh, a bit like an operating theatre. The main thing to remember is that it can make a big difference, and getting it wrong is just a pain in the rear. My first bathroom install lasted less than 24 hours before I put the old bulbs back!

The second mistake I made was underestimating the quality and design of the original lighting. Having lived with it for many years, when I started to replace elements of it, I found that I really missed them! Not only the lighting, but the feel and temperature as well. This is the main reason why I have retained nearly all the original lights in my present installation. I think one of the reasons for this is that most of us grew up with the look and feel of the old style lighting - both incandescent and fluorescent. Am I the only one who so often goes into a pub or restaurant which has just had all it's bulbs replaced willy nilly with modern bulbs, and gone "ouch!"?

So what's the appeal? Power saving! You are all mostly shouting. Well I have looked into this quite deeply, and I just don't think the power saving is all that great, or that important. Most Classic Hymers have a combination of 12v strip lights, and small round halogen spots. The strip lights are quite efficient, about 1 amp, and the spots less so at about 2 amps. On paper the difference is quite big, but in reality? I can't imagine a situation where you would have all the lights on for 6 hours. So the lighting "bill" for an average evening might be in the order of 10 amps. Yes the led's might only consume 20% of that - but so what? You have at least a 100 amp battery - you can afford it! And the real deal changer in recent years is that fact that the vast majority of us now have solar panels or some sort, which start to work as soon as the sun comes up, putting power back in.

As an example - take the 4 bulb bathroom column in most Classics. Switch it on and watch the rest of the lights in the van dim, and watch the needle zoom into the red! But Hymer always did things for a reason. You need light to do your makeup (Jon Avery!). As soon as you do away with those 4 powerful bulbs, you will miss them! And the reality is that Hymer didn't bother about how much power they used because they would only be on for a short time. They might use 6 amps - but for how long? So think about this before you rip them out.

My contention is that it isn't how much power you save, but how you use the power available. 

Power saving through lighting is only really a big factor if you are spending a lot of time off grid, and in particular in winter, where there is less sun available.

I am not trying to put anybody off LED lighting, but I do think there is more to think about than just power saving.

Finally, here are some random thoughts about LEDs.

Led strips in the curtain pelmets look super! But you have to install them properly. Nearly all the self adhesive strips I have used have eventually started to come down after a year or so - it can be very frustrating. You have to clean the surface very well, and basically if it doesn't say 3M on the backing strip - don't use it! You can repair falling strips with hot melt glue, or other glues, but it's a fiddly job.

RBG strips that change colour are very funky, but not as replacement lighting. The white that they produce is not liveable with. I suggest RGB strips for decoration and entertainment only.

LED bulbs that consist of lots of leds in clusters are, only in my opinion, the most potentially disappointing of all. Just one faulty flashing led and the thing becomes a source of annoyance. There have been gazillions of cheap Chinese led bulbs on the market, and already I reckon most of them are in the bin. If you have to use bulbs, buy the best you can possibly afford.

Quality in general can be pretty bad. On the whole I have been disappointed with the quality of the components I have used over the last few years. Last year I decided to go in the opposite direction and seek out the most expensive gear I could find - the sort used by proper fitters in commercial establishments. So far a year has gone by without a single fault. So you get what you pay for. Bear in mind that you really only want to do the job once! 

If you are getting on a bit, and find that you need more light than you used to for close up work, then well installed, powerful, high quality, dimmable, warm white led strips can be an absolute boon - especially over the kitchen and dining area.

So in conclusion, think twice, plan your installation, use the highest quality you can, think carefully about the aesthetics and don't be obsessed with power saving.

Also

On the subject of the original Hymer tube lights - most of us have one in the bedroom and one in the van. These were (I think) made by Philips, and are no longer available. However they are a lovely design, and part of the Classic look. They don't consume a lot of power, and have a nice light. The tubes can be replaced, but when the transformer goes, as many do after 25 years, then it's quite a wrench to replace them with a modern unit. However it is a very worthwhile project to rip out the insides and install warm white led strips inside. The end result is very good, and preserves the "classic" feel.

More musings on buying vans (clipped from FB)

I've had 2 S700's in the last 15 years and I love them. Assuming you are not afraid of a toolbox and rolling your sleeves up, then this is my advice. You won't find a perfect van, so it's a matter of how much money and work you are willing to commit to any given van. Most things in a van are cosmetic and not worth getting worried about, as long as the price isn't daft. Batteries, appliances, fridges, wiring, front dash board etc are all reasonably straightforward DIY jobs, and there is usually plenty of work to be done, unless it's been kept on top of by a previous owner. So what you are really looking for is a van that just "feels right" - something that can be worked on - a vision. At a basic level it is a box on wheels, so it's the box and the wheels that need to be looked at most carefully. Look at the expensive things. You want an engine that sounds quite sweet and isn't leaking oil, although some oil leaks can be easily fixed. A bit of smoke from cold is fine and should fade away. Check an auto box very closely, it is imperative to have a test drive. The van should move smoothly through the gears, and kick down on hills. You want progressive acceleration up to 50-60 and then a reasonably smooth cruise - these vans are not fast. Manual boxes should select all gears normally, but don't worry about 1st gear being stiff and difficult to engage. It's a crawler gear and designed to be selected at standstill. If the stick feels spongy and sloppy then it's usually the selector mechanism, not the box itself, and easily fixed. I have written another article about this on this blog. Steering should be reasonably tight and vibration free, but problems here are usually just a matter of worn bushes and easily fixed.

Next, use your nose and smell for damp. Old Hymers are generally watertight unless they have been damaged or abused. 

Around the front end drivers door, if it has one, and the dash board - which is a favourite for getting rotten - it's a piece of plywood and gets soft from all the condensation that drips down the inside of the windscreen. It's a weekends work, and pretty much every old Hymer needs it done at some stage. A knowledgeable seller will tell you if it's been done, but if not, rock the van from side to side, inside, and if you see any movement between the bottom of the windscreen and the dash board, then you know it will need doing. It shouldn't be a deal beaker if you like the rest of the van and are handy with tools, a drill and a jigsaw.

Then take a good long look underneath - you are looking for any areas of bad rust on the main chassis members. Hymers were very well undersealed at the factory, so don't be suspicious if you find it surprisingly clean, but occasionally you will find chassis members flaking with rust, especially behind the back wheels. If the van has mudflaps at the back wheels, that's a good sign. Also check the rear of the floor right at the back in the boot - it gets rotten with all the road water.

Also - these vans have character. Just sit in it quietly for 5 minutes and imagine yourself living in it. Hopefully it will whisper to you!

Price wise - The Germans are asking around £16k for fully loaded lovingly maintained examples. For this sort of money it should be perfect. More than perfect! Most UK vans that need a bit of TLC are around £10 to 13k. Maybe a bit more at this time of year. The right price should be the purchase price plus whatever you need to spend to get it up to scratch, so if you have a fixed budget bear this in mind. If you find any areas of concern and need advice, take pictures and an audio recording of the engine and come back on here. Good luck! 

Why is it often difficult or even impossible to select 1st gear on the Mercedes box?

RONS'S TECHNICAL TIPS No 5 speed box

I have just been asked (again) why is the pre 95 Mercedes gearbox so difficult to get into 1st gear. Fiat owners will take comfort that just as they have an occasional problem with 5th, the Merc 1st gear is also an awkward child.

This is a long read, so if you have no interest in the intricacies of a Mercedes gearbox then get on with your life now!

QUESTION - Ron I am finding 1st a little tough sometimes. Not crunchy just seems a tighter gate than the rest. It's getting better as I get used to it. It doesn't jump out or anything. I have also found a "false gear" to the left of 1st. Is this something you have fixed or got used to? Cheers, Julian.

ANSWER - 

Yes it is exactly as you describe. First is stiff and awkward, but not temperamental - you can master it. The reason it is stiff is that it is a very low gear and spinning very fast even in relation to the engine speed at tickover, so the synchromesh rings have a lot of work to do to spin the gear up to speed before it can be engaged, and so are manufactured bigger and tougher on 1st gear for this reason, and so need more pressure to engage. It shouldn't be a problem because 1st is a crawler gear and usually always engaged when stopped. You just have to maintain pressure on the stick a moment longer to allow the gear to spin up, and then it should engage smoothly. The false gear you refer to is no mans land between 1st and reverse. !st is slightly to the left and back, reverse is fully to the left and forward. The stick naturally rests between 2nd and 3rd. If you push the stick towards the left you will feel 2 resistances, the first is where you pull back to 1st, and the second, further over, is a full stop, and will only go forward into rev. The trick is to know these two positions, and not to make the mistake most people make, which is to ram the stick all the way to the left and then pull back expecting 1st. This reason and this reason alone is why people accuse the Mercedes box of being a bitch. This is a bit unfair as it is actually a bullet proof box, it just has "character"! The most you can criticise it is that it is old fashioned compared with modern boxes, which are silky smooth, and have well defined gates (the layout of the gears). 

However on a very steep hill, you may find yourself wanting to do a moving change down from second to first - it is a rare situation, so doesn't get much practice. Basically, as others will testify, it is an almost impossible change. It has to be done quickly, or the van will stop, so it get's rushed and fluffed. As I said before, if 1st gear is spinning fast on tickover, then with the engine revving highly climbing a hill in 2nd then it is spinning even faster, too fast even for the synchromesh rings to have any chance of spinning the gears up to a speed where they match each other and can engage smoothly. So it refuses to go into first and the van stops on the steep hill and you have to engage the handbrake quickly, then select 1st and smoke the clutch to pull away again, and then remain in 1st and crawl up the hill at 10mph as you are afraid to change gear!

The answer to this is to master the ancient and lost art of double declutching. Baby boomers (and their parents) should remember the days before synchromesh when all boxes were "crash" boxes. But before I describe double declutching, I have to describe what synchromesh is. Most people know that a gearbox has cogs inside of different sizes to allow the same speed of engine revs to deliver a range of different road speeds. But when you want to change gear, the cog that is connected to the engine, is spinning much faster (or slower) than the next cog of the gear you want. If you try to push two cogs together that are spinning at different speeds, then of course you get that familiar grinding sound. The only way to get a smooth change is to match the speeds of the two cogs before pushing them (engaging) together. This used to be a matter of pure skill. Drivers had to be intimately aware of the speed and sound of every gear in relation to road speed and to skilfully use the accelerator (and the clutch) to match the speed of the engine cog to the speed of the next gear cog. They did this by either letting the engine revs fall, changing up (easy) or increasing the engine speed, changing down (hard). The trick was to gently let the gears just touch each other with hand pressure on the stick and feel the vibrations of the gears and as soon as they matched up, push in the gear smoothly - pure skill! After WW2 and through the 1950's as cars became common for non professional drivers, Porsche and others eventually came up with a much better system, known as "synchronised shifting" or synchromesh. This is an extra mechanism in the gearbox that does mechanically what the driver used to do by skill - it matches up the gears perfectly before engaging them, using an interlocking system of spinning rings and cones. When you change gear in a synchro box, the slight resistance you feel as you enter a gear, especially on older cars, is the synchro doing it's job. Nowadays it's all computer controlled, but not on Classic Merc Hymers!

It should also be said here that the selector mechanism - the system of rods and joints that connects the bottom of the gearstick to the selector arms on the side of the gear box - is also an important part of this setup, and should be kept well lubricated and maintained - 90% of the time when people think they have a bad box - it's just an easy fix to the selectors. If your gear change is very stiff, or sloppy like a bag of spanners, then your selectors need sorting out - an easy job.

So, back to double declutching! Synchro can only achieve so much, usually the differences in speeds between gears are not so much, so changes are easy and smooth. But in the case we are discussing - down in 2nd and 1st where the engine is revving highly, the speed difference is too much to allow the change in the time needed, hence the resistance, and difficulty in getting into 1st. To get round this and effect a smooth change - yes it is possible - you have to use a trick from the old pre synchro days, known as double declutching. You depress the clutch, pull the stick back from 2nd into neutral, and just hold the stick with gentle backward pressure right at the point where it should go into 1st, then lift the clutch, blip the accelerator, which revs up the engine, and then depress the clutch again and slip into 1st when you feel the resistance drop - all in one easy fluid motion that takes only slightly longer than a normal change down. This has the effect of spinning up 1st gear and making the change much easier. In fact it is basically the only way to make a moving change into 1st gear on the Mercedes box (pre 95). And this is the main reason, if not the only reason, the box has a bad reputation, because all the other gears are pretty much silky smooth. 3rd to 2nd is occasionally similar, especially when flogging up a hill, and this change can also be made smoother by ddc'ing.

It is a difficult manoeuvre to perfect, but not impossible, it is similar to a dance move - coordination of hands and feet movement. This is why you often hear trucks (in the old days) making that familiar sound as they came to a hill - the engine revs fall, then he changes gear with that familar blip of the accelerator, and then the engine revs resume at a higher note. Almost impossible to describe in words, but instantly recognisable if you hear it (and are old enough).

It is a vey satisfying technique to master, and it is essential if, like me, you want to really push your Hymer up the steepest of hills and hairpins, like Hardknott pass in the Lake District, and the even more spectacular minor Alpine passes. A fully loaded S700 or S660 just doesn't have the guts to get up a 1 in 3 in 2nd gear, especially if there is a hairpin coming, so you have to be able to get into 1st quickly and smoothly and with the minimum of loss of speed. The only other alternative is to know the road and what's coming, and select first from the bottom, and grind up in 1st without changing gear. Also there is no shame in having to stop to engage first on a steep hill - you have a right to be there so the guy behind in his Audio Quattro paddle shift computer controlled 6 speed auto box in sport mode can basically sod off!

Fridge problems?

Ron's Technical Tips number -10 degrees

FRIDGE PROBLEMS

It's the time of year when our vans come out of storage and many of us have fridge problems.

What most of us have to remember is that our fridges are quite often original, and that makes them over 20 years old. Not many home appliances last that long, so it's not surprising that we get a lot of fridge problems.

Here in very simple terms is how your fridge works. At the back there is a chimney. At the bottom of the chimney is a gas burner, heat from the flame goes up the chimney and passes into the tubes that contain a chemical, which converts the heat into cold - very simple explanation.

Also in the chimney are two heating elements - one powered by 240v and the other by 12v. So there are 3 possible sources of heat to heat up the chemicals.

The commonest problems are the fridge not working on any of these 3 sources, so we will discuss each one in turn.

Gas. The commonest fault is that soot and or crap falls down the chimney and onto the burner which either restricts the flame, or preventing it lighting at all. This is quite easy to fix, as long as you can get access to the burner assembly, usually but not always through the lower ventilation panel outside.

The next problem with gas is that it won't light. It acts just like a cigarette lighter - you press the button, the gas is switched on, and a spark ignites the gas. However unlike a cigarette lighter, when you take your finger off the button, the gas should stay ignited. This is because there is a safety feature called a thermocouple. This is a little finger of metal that is placed in the flame, and if it gets hot, as it should, then it operates a gas valve that keeps the gas flowing. If the gas goes out, it cools, and shuts off the gas. If the gas lights, but goes out when you take your finger off the button after about 20 seconds, then it is usually the thermocouple. The thermocouple is a fundamental safety feature.

The next problem is no spark. When you try and ignite the fridge there is usually a tick tick sound which is the spark. There is another little finger of metal placed in the burner that allows the spark to jump between it and the burner body, again just like an electronic cig lighter. If there is no power getting to this, or the spark can't jump because of crap and soot in the burner, then it won't light.

Finally - there just might not be any gas at all! After storage with the gas turned off, there may be no gas in the pipes, or it might take a while to come through. You have to be patient. Sometimes it's a good idea to light the cooker to promote the gas flow through the pipes, and do remember to make sure all the relevant gas valves are open.

Electricity. Both 12v and 240v elements work on the same principle - just like a kettle element. Power is applied and the element gets hot. Other than making sure the fuses are OK, there is very little to go wrong and if it doesn't work then usually the element has given up the ghost and needs replacing. Occasionally you get a faulty switch, which can be hard to troubleshoot without access to the back of the switch and the use of a multimeter.

Don't forget that in a correctly wired van, the fridge will only work on 12v when the engine is running. If everything else works fine, but you are not getting cooling while driving, assuming it is actually switched on to 12v, the the commonest reason is that the relay which switches 12v from the engine alternator to your fridge is broken. This relay is usually to be found behind the main habitation fuse panel. You should also remember that the 12v element is the weakest of all the heat sources, so the fridge will be less cool when driving than it will be on gas or 240v.

If the fridge is working but not getting cold, or just getting cold at the top, near the freezer box, then this usually means the chemicals have got separated in the pipes. There are various techniques to try and fix this and Peter Curry is our resident expert. 

There are plenty of how to fix videos on Youtube and lots of previous posts on this group, if you are a DIYer, and we have resident experts and recommended engineers to help you out if you are not.

Don't mess with gas unless you know exactly what you are doing - it is quite an easy job to clean rubbish away from the burner, but anything that involves undoing actual gas fittings or pipes should be done by a trained gas man. Replacing elements is also quite a tricky job.

Finally - we all like to keep our vans original, but fridge problems are one of the commonest problems we find on the group. A temperamental fridge can ruin an otherwise perfect summer trip. Nothing lasts forever, so sometimes it's just best to chuck in the towel and buy a new fridge. The new Dometics are a lot better than their grandfathers, colder and more efficient. I gave in and bought a new fridge last year and we love it. But they ain't cheap! But don't give in unless you have had a proper opinion from an expert.

Stay cool people!

UPDATE - more information about the absorption mechanism by Peter Curry

Never turn your fridge upside down it will just pour all the sludge from the resevoir into your evaporation jet. what people are trying to do when they do this is to remix the chemical cocktail that is the driving force that makes your fridge cold.

There are much easier methods to try first , with fridge removal being a final option ready for rotating the fridge to mix the cocktail.
And even this is done in a prescribed manner and direction.
PLEASE DO NOT REMOVE YOUR FRIDGE AND STAND IT ON ITS HEAD you are taking a chance with the odds being about 35% for you and 65% against you.

If fridge has been stood for a while and will not get cold after being on on gas for 24hrs with good flame and flue then there are two possibilities.

1 the fridge is no good buy a new one
2 the chemical cocktail that runs the fridge has sperated out

These are chemicals that once mixed live reasonably happily in a cocktail but once seperated need some encouregment to join to gether again.
Put fridge on gas and if not single energy selector type, put the mains on as well and turn both to full, leave for 4 to 6 hours then turn fridge to 12v and take the van for a drive down a rough road - you are looking for vibration not bloody great potholes! About 1/2 hour is enough,
Then go home put fridge on gas and leave over night.
We have a 90% success rate with this.